Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Reexamination Certificate
1999-02-23
2001-05-29
Allen, Stephone B. (Department: 2878)
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
C073S861710
Reexamination Certificate
active
06239446
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to flow sensors and more particularly to electronic sensors useful in monitoring water flow in fire prevention systems such as sprinklers.
BACKGROUND OF THE INVENTION
Water flow switches for sprinkler operation indication have been available for decades. Over the years a single design has evolved which consists of a switch body, a snap-action switch, a plunger which extends into the sprinkler riser and a paddle assembly which is connected to the switch body via a pivot. The paddle partially obstructs the cross-section of the pipe. When water begins to flow the paddle swings down-stream, rotating about the pivot. A cam on the paddle depresses (or releases, depending upon the design) the plunger which transmits the motive force of the paddle into the switch interior. The movement of the plunger actuates, either immediately or through a mechanical time delay called a “retard”, the snap-action electro-mechanical switch, providing an electrical signal to the fire alarm control panel.
There have been a number of persistent problems with this design. The plunger must be sealed with either rubber boots or o-ring seals to prevent the leakage of water from the sprinkler pipe interior into the switch interior. This need for a sealing force results in the need for relatively large mechanical forces on the paddle. However, large required forces on the paddle result in the need for commensurately large hydraulic forces due to water flow. These large forces necessitate large water flows before the reliable actuation of the switch can be achieved. In addition, the occasional oscillation of water within the sprinkler system due to pressure fluctuation in the public utility water mains necessitates a “retard” feature. This requires the introduction of a time delay between the operation of the sensing paddle and the actuation of the electro-mechanical switch. The current state of the art relies on mechanical time delays to implement the “retard” feature. This adds to the complexity and cost of the flow switch as well as reducing its inherent reliability.
It is also desirable to provide a capability to measure a particular flow rate of the fluid in the conduit. The use of inherently reliable solid state circuitry to accomplish this is a further contribution of this invention.
In 1996 this inventor developed an Electro-Optical Valve Status Supervision Switch. U.S. Pat. No. 5,584,319 was issued on Dec. 17, 1996 for this invention. This invention utilized a reflective pit on the stem of an outside screw and yoke valve situated opposite an LED/phototransistor pair to monitor when the valve was not fully open. This development is helpful in implementing the objectives of this invention.
It is therefore a primary object of this invention to provide a fluid flow detection device having a passive interface between the signal sensing portion and the signal generation portion and the flow responsive element wherein the signal generation and sensing portions employ reliable, solid state electronic circuitry.
It is a further object of this invention that the detection device include reliable electronic circuitry to distinguish between fluid flows that are of sufficient amount and are continuous for at least a certain minimum amount of time.
It is still a further object of this invention is to employ the fluid flow detection device of this invention to detect water flows in fire protection sprinkler systems.
It is yet another object of this invention to employ certain elements of a flow responsive element presently used in the art, but which is adapted to accommodate the signal generation and sensing functions of the present invention.
A still further object of this invention is to provide a fluid flow detection device which can sense and indicate specific fluid flow rates.
SUMMARY OF THE INVENTION
Towards accomplishment of these and other objects which shall become apparent from consideration of the accompanying drawings and this detailed accompanying description, there is disclosed a fluid flow detection device for detecting the flow of fluid in a conduit such as water in a piping system supplying fire suppression sprinklers. The device disclosed includes a sensing element including a portion having a reflective surface that is situated in the fluid whose flow is to be sensed. The sensing element is positioned in the conduit utilizing a mounting element which permits the sensing element to rotationally move. The sensing element in response to the flow of fluid moves from a steady or quiescent position to a second displaced position. Of course, the reflective surface also moves. An optical illuminator such as an LED is electrically energized to produce an incident optical signal. The illuminator is fixed in position relative to the sensing element and the reflective surface, so that the optical signal from the illuminator passes through a portion of the fluid whose flow is to be detected, such that a reflected optical signal depends on the position of the sensing element, and the reflective surface, in relation to the incident optical signal. The characteristics of the reflected signal can vary depending on the characteristics of the reflective surface.
When in position where the incident optical signal is reflected, the resulting reflected optical signal is received by a optical responsive receptor. The responsive receptor includes an input portion such as a photo cell which recreates an electrical signal at the output of the receptor which is then processed. In one embodiment, the electrical signal at the receptor output includes a first and second condition, i.e. a first condition indicative of presence of the reflected optical signal; and a second condition indicative of the absence of the reflected optical signal so as to distinguish the movement of the sensing element from a first position to a second position in response to fluid flow irrespective of flow rate. An indicator which in the preferred embodiment is an electronic circuit processes the receptor output signal and produces an appropriate indicator signal to indicate the presence or absence of the reflected optical signal and thus the position of the sensing element of either one of two conditions to thereby signify the flow of fluid.
The preferred embodiment describes electronic circuitry including an oscillator which produces an oscillator output signal to energize the optical illuminator such as the LED. The oscillator output signal of the preferred embodiment includes a signal predetermined pulse width and period, and of known phase. As such the incident optical signal from the output of the LED tracks the oscillator output signal as to phase, pulse width and pulse period as does the reflected optical signal. In the preferred embodiment, the optically responsive receptor is a photo cell. Further in the preferred embodiment, a phase comparator circuit is use to produce a phase comparator output signal in response to the comparative sampling of the oscillator output signal and the responsive receptor output signal. The comparison of the two inputs produces a comparative output signal only when the receptor output signal is in phase with the oscillator output signal to thus avoid an indicator signal in response to spurious signals.
Further, a timing circuit is described which is adapted to respond to the presence to the receptor output signal to produce a change in the indicator signal indicative of the change in the receptor output signal from the first condition to a second condition after a predetermined minimum period of time. This circuit exists to obviate responses to sensing element movements due to flows that result from pressure changes, etc. in the conduits, or circumstances other than an opened sprinkler head.
The fluid flow detection device of the present invention also includes an adaptation wherein the actual flow rates of the fluid in the conduit can be approximated. This facilitates the tracking of the progress of a fire as represented by increased water flow in additional s
Allen Stephone B.
Quast, Esq. W. Patrick
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